I really feel this varies by each congregation. I have been to small congregations that were not very friendly. I have been to large congregations that were friendly. A LOT of this has to do with the pastor/ministerial team. If they model friendliness and sincere church hospitality, the church follows them. Also, especially with the youth, sometimes this must be taught from the pulpit for a while for it to 'catch on' in the church.
I'll give it this, in a smaller congregation, it's easier to find a niche where your help is easily used, and not feel you are treading on toes. In larger congregations, frequently there is someone who already has been doing whatever, since that church started, and sometimes such a person is very prickly about someone else even helping.
I am the ASL interpreter for my church. And if someone comes, who signs even a little, I'll put 'em to work. I don't want anyone feeling that "Well, this is HER place, and no-one else can do this" I hope that we have enough 'terps that should I have to move, become sick, etc. the ASL program would continue without a hitch.

No, that's why we attend a small rural church. Smaller churches seem to exist to help folks. Large ones are all about getting more money and building huge "campuses". What a waste, not what Jesus would do.